Drug delivery devices for setting and dispensing a single or multiple doses of a liquid medicament are as such well-known in the art. Generally, such devices have substantially a similar purpose as that of an ordinary syringe.
Drug delivery devices, in particular pen-type injectors have to meet a number of user-specific requirements. For instance, with patient's suffering chronic diseases, such like diabetes, the patient may be physically infirm and may also have impaired vision. Suitable drug delivery devices especially intended for home medication therefore need to be robust in construction and should be easy to use. Furthermore, manipulation and general handling of the device and its components should be intelligible and easy understandable. Moreover, a dose setting as well as a dose dispensing procedure must be easy to operate and has to be unambiguous.
Typically, such devices comprise a housing or a particular cartridge holder, adapted to receive a cartridge at least partially filled with the medicament to be dispensed. The device further comprises a drive mechanism, usually having a displaceable piston rod which is adapted to operably engage with a piston of the cartridge. By means of the drive mechanism and its piston rod, the piston of the cartridge is displaceable in a distal or dispensing direction and may therefore expel a predefined amount of the medicament via a piercing assembly, which is to be releasably coupled with a distal end section of the housing of the drug delivery device.
The medicament to be dispensed by the drug delivery device is provided and contained in a multi-dose cartridge. Such cartridges typically comprise a vitreous barrel sealed in distal direction by means of a pierceable seal and being further sealed in proximal direction by the piston. With reusable drug delivery devices an empty cartridge is replaceable by a new one. In contrast to that, drug delivery devices of disposable type are to be entirely discarded when the medicament in the cartridge has been completely dispensed or used-up.
In particular with users or patients being physically or visually impaired correct handling of the device is sometimes cumbersome. Typically, such devices comprise and provide visual or readable indicators or display elements in order to inform the user or patient of the actual status and configuration of the device. Such information should be clearly and unambiguously legible, even for visually impaired persons.
Document WO 2013/050461 A1 discloses a display arrangement for a drug delivery device comprising a first display member with numerous surface portions having at least two different but interrelated appearances and being alternately arranged along a first direction. The display arrangement further comprises a second display member with a light modulating structure to modulate visible light emanating from the first display member. First and second display members are moveably disposed relative to each other to simultaneously reveal and/or to conceal at least two surface portions of interrelated appearance.
With drug delivery devices such as for instance described in EP 1 603 611 B1 a dose dial sleeve can be rotated with respect to a housing until a desired dose value is visible through a window of said housing. Upon selecting of a dose the dose dial sleeve is rotated and extends from a proximal end of the housing since it is threadedly engaged with the housing via a helical thread. It may then happen, that various symbols or indicia provided on the dose dial sleeve also extend from a proximal end of the housing. A user of the device may get confused by multiple indicia appearing in the window as well as beyond a proximal end of the housing. It may arise, that the user misinterprets the respective symbols or numbers that appear beyond the proximal end of the housing and that the user consequently selects or dials an inappropriate dose.